LONDON (Reuters) - British prosecutors weighing whether to take action against those who assist in the suicide of a terminally ill loved one should focus on the motivations of the suspect, according to new guidelines issued on Thursday.

The guidelines, which do not amount to a change in British law, stem from the case of Debbie Purdy, a woman suffering from multiple sclerosis, who sought clarification from the courts on whether her husband would be prosecuted for helping her to die.

The case was one of several in recent years that have prompted an ethical debate on assisted suicide, which under British law is punishable by 14 years in jail.

Advocates of the right to die say it is inhumane to go after people for helping a loved one take their own life with dignity. Critics say tolerating assisted suicide could lead to vulnerable people being bullied into suicide by self-interested relatives.

The new guidelines list 16 reasons for prosecuting and six reasons for not prosecuting. One of the factors that could justify a prosecution was a situation in which the person who assisted in a suicide stood to gain financially from the death.

Among the factors against prosecuting were evidence that the suspect had sought to dissuade their loved one from suicide, and that the terminally-ill person had "reached a voluntary, clear, settled and informed decision to commit suicide".

Since 1992, about 100 Britons have ended their lives at the Dignitas facility in Switzerland, where assisted suicide is legal, without their relatives being prosecuted.

NO ASSURANCE YOU WILL NOT BE PROSECUTED

Purdy said the guidelines would allow her to live longer because they made clear her husband would not be prosecuted, but called for a change in law to decriminalise assisted suicide when it was a merciful act and there was no malicious intent.

"(The guidelines) mean I can leave it until I physically can't do things myself to be able to ask for assistance, so my life is saved ... But we need a new law," she told Sky News TV.

The guidelines were issued by Keir Starmer, director of public prosecutions, after Britain's highest court last July asked him to clarify the factors that would determine whether to prosecute a person in the position of Purdy's husband.

"Nothing in the policy can be taken to amount to an assurance that a person will not be prosecuted," Starmer said.

He stressed that the guidelines did not open the door to so-called mercy killings, in which a person kills a loved one who wants to die but is unable to commit suicide. These fell under the category of manslaughter or murder, Starmer said.

He said the main novelty was a change of focus from the characteristics of the deceased to the motivation of the person who helped them die. This was a complex assessment that had to be done on a case-by-case basis, he said.

"Assessing whether a case should go to court is not simply a question of adding up the public interest factors for and against prosecution and seeing which has the greater number. It is not a tick box exercise," Starmer said.